Shuttle transfer systems have been known in the art which are controlled to position a tool or assembly component in a specified position in one, two or three axes. Exemplary of such a system is U.S. Pat. No. 4,836,111, issued Jun. 6, 1989 in the name of Kaufmann wherein positioning is controlled by a rack and pinion drive. However, it has been determined that accuracy by a rack and pinion drive is minimal, and many applications require a higher accuracy.
U.S. Pat. No. 4,600,358, issued Jul. 15, 1986 in the name of Graf discloses a manipulating device operating in two axes wherein the drive is provided under computer control via a gear rack and pinion. A position sensing transducer with a pulse generator is provided on the control of the drive. This sensor is a prestressed sensor pinion engaging the corresponding gear track to provide position information. This type of sensor which is engaged on the driving track also can be inaccurate with respect to the positioning of the workarm or tool thereon.
U.S. Pat. No. 4,843,708, issued Jul. 4, 1989 in the name of Yokoi et al discloses an assembling system for assembling an automotive engine and transmission which are supported on lifter tables and are controllably moved to change the location thereof in response to positioning detectors comprising CCD cameras. However, there is no shuttle movement, and use of cameras can be expensive and complex.